JP5252275B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a fax machine that employs an electrophotographic system.

  In an electrophotographic image forming apparatus, most of the toner developed on a photoconductor as an image carrier is transferred to a transfer target or a recording material, but a part of the toner is not transferred onto the photoconductor. Remains. Conventionally, a cleaning means for collecting and discarding the transfer residual toner has been provided. However, from the viewpoints of cost reduction, downsizing, effective use of resources, etc., several cleanerless image forming apparatuses that collect and reuse the transfer residual toner by developing means without collecting and discarding it have been proposed and put into practical use. Has been.

  In the cleanerless system that does not have a cleaning unit that collects and discards the transfer residual toner, more toner comes to the charging unit while remaining on the photosensitive member than in a system that has a normal cleaning unit. For this reason, the toner adheres to and accumulates on the charging means, and there is a possibility that abnormal charging occurs due to non-uniform charging. There are several methods for charging the photoconductor, but the roller charging method that charges the photoconductor by contacting a conductive charging roller with the photoconductor is environmentally friendly (for ozone generation), space efficiency, and charging stability. Widely used from the viewpoint of sex and the like. However, since the charging roller is in contact with the photoconductor, the transfer residual toner on the photoconductor is likely to adhere to the charging roller, and the toner adhering to the charging roller may be applied to the roller surface over time due to friction and pressure with the photoconductor. It will stick. If the surface resistance becomes non-uniform due to toner fixation, there is a possibility that the photosensitive member cannot be uniformly charged and a streaky or band-like abnormal image is generated.

  For this reason, a method of removing the cleaning member by contacting it with the charging roller is used. However, if toner accumulates on the cleaning member, there is a possibility that the cleaning performance may be drastically deteriorated, and the toner needs to be removed from the cleaning member. It becomes. In the cleanerless type image forming apparatus described in Patent Document 1, the amount of charge remaining on the photoconductor so that the residual toner on the photoconductor is aligned with a normal polarity, and the charge amount can develop the electrostatic latent image on the photoconductor by the developing means. The charging control means for controlling so as to become is installed. As a result, the transfer residual toner remaining on the photoconductor after transfer is difficult to adhere to the charging roller in contact with the photoconductor, and the transfer residual toner on the photoconductor that should not be developed is collected by the developing means. The Further, a configuration has been proposed in which a cleaning film is provided on the charging roller, and the toner between the cleaning film and the charging roller is made to have the same polarity as the charging roller by frictional charging so as to easily transfer from the charging roller to the photosensitive member. How to prevent the toner from adhering to the charging roller and how to remove the toner adhering to the charging roller are major issues in extending the life of the charging roller.

  On the other hand, in the cleanerless type image forming apparatus described in Patent Documents 2 and 3, a method is proposed in which the charging roller is installed in a non-contact manner with the photoreceptor so that toner does not adhere to the charging roller. Patent Document 2 proposes a charging roller that is arranged in a non-contact state with a photoreceptor, and has a difference in electrical resistance between the surface of the charging roller and a portion near the surface. In this charging roller, the discharge to the photoreceptor does not occur at the portion corresponding to the highest resistance portion, but mainly occurs in the low resistance portion, so that the electrical characteristics are stabilized over time and charging unevenness is reduced. Can do. Patent Document 3 also proposes a method in which the charging roller is arranged close to the photoreceptor so that a gap larger than the toner particle diameter is formed. Here, a cleaning roller is provided upstream of the charging roller in the rotation direction of the photoconductor for collecting the transfer residual toner on the surface of the photoconductor by electrostatic attraction. At times other than the time of image formation, the polarity of the potential difference between the cleaning roller and the photosensitive member is switched to adhere the collected toner to the photosensitive member, and the developing roller collects the toner.

JP 2001-215799 A Japanese Patent No. 3442574 JP 2001-249525 A

  However, even if the charging roller is installed in a non-contact manner with respect to the photoconductor as in Patent Documents 2 and 3, the toner on the photoconductor gradually adheres to the charging roller and accumulates. Depending on the conditions, there may be a case where uniform charging cannot be performed at around 1000 sheets.

  Therefore, as a result of extensive investigations by the present inventors, the charging member is arranged in a non-contact manner with respect to the photoconductor, and a voltage containing an AC component is applied, thereby greatly improving the contamination of the charging member over time. I found out that This is because the toner adhering to the charging member oscillates and flies by the AC voltage, returns to the photosensitive member, and can be self-cleaned by the charging member itself. On the other hand, by using a non-contact charging method to which a voltage containing an AC component is applied, the charging roller is at a level where there is no problem with the contamination of the charging roller. The effect scattered by the member is also reduced. For this reason, in a region where the transfer rate of the toner image is poor, the transfer residual toner is sent to the charging member in the form (pattern) as it is with the previous image remaining. The charge distribution of the toner after passing through the charging member is shifted to the weakly charged side due to the influence of the AC voltage of the charging roller regardless of the charge distribution at the time of input to the charging member. As the toner is weakly charged, the mirror image force between the toner and the photosensitive member is also weakened, so that the development recovery of the toner is enhanced. However, if the amount of transfer residual toner input to the charging roller is remarkably large, there is also a strong regular charged toner, which is difficult to collect. This normally charged toner that could not be collected causes afterimages.

  In a conventional cleanerless image forming apparatus, in order to prevent toner from adhering to the charging member, a brush or the like that performs charging control of the transfer residual toner upstream of the charging member in the photosensitive member moving direction is used. A charging control means is installed. On the other hand, in the present invention, since the charging member is disposed in non-contact with the photosensitive member and a voltage including an alternating current component is applied, contamination of the charging roller is a problem regardless of the charge distribution of the input toner to the charging member. Don't be. In other words, in the present invention, there is an advantage that charging control of a brush or the like is not necessary, and a toner scattering member to be described later may be designed exclusively for the function of scattering, and strict charging control like a charging control unit is required. Do not need.

  The present invention has been made in view of the above problems, and an object of the present invention is to eliminate the occurrence of abnormal images due to contamination of the charging member in the cleaner-less image forming apparatus and to prevent residual images due to transfer residual toner. It is an object of the present invention to provide an image forming apparatus capable of stable image formation without occurrence over a long period of time.

According to the first aspect of the present invention, there is provided an image carrier that carries an image, a charging unit that charges the image carrier, a latent image forming unit that forms a latent image on the image carrier, and a latent image of the image carrier. An image forming apparatus comprising: a developing unit that supplies toner to a toner and develops the toner and collects toner remaining on the image carrier; and a transfer unit that transfers a toner image of the image carrier to a transfer target. The charging unit is disposed in a state where the charging member is not in contact with the image carrier, and charges the image carrier using a discharge generated by applying a voltage in which an alternating current component is superimposed on a direct current component, A toner scattering member that disperses residual toner remaining on the image carrier without being transferred by the transfer unit is located upstream of the charging unit in the moving direction of the image carrier, and is more upstream than the transfer unit. The toner scattering member provided on the downstream side in the moving direction , It is characterized in that the contact pressure of the image bearing member in the image forming region or an image portion is larger than the contact pressure of the image bearing member of the paper or between the non-image portion.
In the present invention, in order to charge the image carrier, the charging member is arranged in a non-contact state with the image carrier and a voltage containing an AC component is applied. Since a voltage containing an alternating current component is applied to the charging member, the charging member itself can perform self-cleaning, and toner hardly adheres to the charging member. Further, before the transfer residual toner remaining on the image carrier passes through the charging member, the toner scattering member moves the toner with a large amount of transfer residual toner to a small position to disperse the transfer residual toner. Thereby, since the transfer residual toner can be weakly charged by the charging member evenly, the toner recoverability by the developing means is improved, and the occurrence of the residual image is suppressed.

  According to the present invention, in a cleanerless type image forming apparatus, an image can be formed stably over a long period of time without generating an abnormal image due to contamination of the charging member and without generating an afterimage due to transfer residual toner. Is to provide a device.

  Hereinafter, an embodiment in which the present invention is applied to a full-color printer (hereinafter referred to as a printer) that is an electrophotographic image forming apparatus will be described. FIG. 1 is a schematic configuration diagram showing the internal configuration of the printer. This printer uses four color toners, yellow (hereinafter referred to as “Y”), cyan (hereinafter referred to as “C”), magenta (hereinafter referred to as “M”), and black (hereinafter referred to as “K”). A color image is formed.

  First, the basic configuration of the printer will be described. In this printer, an image forming unit 30 including four photoconductors 1Y, 1C, 1M, and 1K as an electrostatic latent image carrier and a transfer device 6 is disposed. In the image forming unit 30, a charging roller, a developing device, a toner scattering member, and the like are provided around each of the photoreceptors 1Y, 1C, 1M, and 1K that are rotationally driven in the direction of the arrow in the drawing. Each of the photoreceptors 1Y, 1C, 1M, and 1K is obtained by forming a photosensitive layer on an aluminum cylindrical substrate having a diameter of, for example, about 30 to 90 mm, and further forming a protective layer on the photosensitive layer. An intermediate layer may be provided between the protective layer and the protective layer. Here, the drum-shaped photosensitive member 1 is taken as an example, but a belt-shaped photosensitive member can also be adopted.

  The transfer device 6 includes an intermediate transfer belt 10 that is stretched and rotated by a plurality of rollers 11, 12, and 13 above the photoreceptors 1 </ b> Y, 1 </ b> C, 1 </ b> M, and 1 </ b> K. The transfer device 6 forms a primary transfer portion by sandwiching the intermediate transfer belt 10 between the photoreceptors 1Y, 1C, 1M, and 1K and the primary transfer rollers 14Y, 14C, 14M, and 14K. In the process of passing through the primary transfer portions for Y, C, M, and K as the endless movement of the intermediate transfer belt 10 occurs, the Y toner images, C on the photoreceptors 1Y, 1C, 1M, and 1K are transferred to the intermediate transfer belt 10. The toner image, M toner image, and K toner image are superimposed and primarily transferred. The polarity of the transfer current applied to the primary transfer rollers 14Y, 14C, 14M, and 14K is positive polarity opposite to the polarity of the toner. As a result, a four-color superimposed toner image is formed on the intermediate transfer belt 10. In addition, the transfer device 15 forms a secondary transfer portion by sandwiching the intermediate transfer belt 10 between the secondary transfer backup roller 13 and the secondary transfer roller 16. In the secondary transfer portion, the transfer paper is sandwiched between the intermediate transfer belt 10 and the secondary transfer roller 16 whose surfaces move in the forward direction and conveyed upward in FIG. The four-color superimposed toner image formed on the intermediate transfer belt 10 is transferred to a transfer sheet at the secondary transfer portion to become a full-color toner image. The polarity of the transfer current applied to the secondary transfer roller 16 is a positive polarity opposite to the polarity of the toner. Foreign matter such as transfer residual toner and paper dust remaining on the intermediate transfer belt 10 after passing through the secondary transfer portion is cleaned by the cleaning device 15.

  Further, below the image forming unit 30, an optical writing unit 7 which is a latent image forming unit is disposed. The optical writing unit 7 irradiates each of the photoconductors 1Y, 1C, 1M, and 1K with a laser beam L emitted based on the image information and performs exposure. By this exposure, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The optical writing unit 7 irradiates the photosensitive member through a plurality of optical lenses and mirrors while scanning the laser light L emitted from the light source with a polygon mirror rotated by a motor.

  A paper feed cassette 20 for storing transfer paper is disposed at the lower part of the printer main body. The transfer paper fed from the paper feed cassette 20 by the paper feed roller 21 is sent to the secondary transfer unit at a suitable timing by a pair of registration rollers 22, and the full color toner image is transferred as described above. Will be.

  A fixing device 23 is disposed on the upper right side of the image forming unit. In the fixing device 23, a fixing nip portion is formed between the fixing roller 23a and the pressure roller 23b. The transfer sheet on which the full-color toner image is transferred in the secondary transfer unit described above is conveyed into the fixing device 23, and the toner image is fixed by pressure and heat received at the fixing nip. The transfer paper on which the toner image is fixed is sequentially stacked on the stack unit 25 by the discharge roller 24. The fixing device 23 is controlled by a control unit (not shown) so that the fixing condition is optimal depending on whether the image is a full-color image or a monochrome image, one side is double-sided, or the type of transfer paper. Here, a fixing device having a heater inside the roller is taken as an example. However, a belt fixing device that travels a belt to be heated, a fixing device that employs induction heating as a heating method, or the like may be employed. it can.

  In a space between the image forming unit 30 and the stack portion 25 above the toner forming unit, toner cartridges 31Y, 31M, 31C, and 31K as developer containers for storing Y, M, C, and K toners. Is housed. The Y, M, C, and K toners in the toner cartridges 31Y, 31M, 31C, and 31K are appropriately supplied to the developing device of the image forming unit 30 by toner conveying means such as a mono pump and an air pump (not shown). These toner cartridges 31Y, 31M, 31C, 31K and the image forming unit 30 can be attached to and detached from the main body of the printer 100 independently.

  Next, the configuration around the photoconductor in the image forming unit 30 will be described. FIG. 2 is a schematic configuration diagram showing the configuration around the photoconductor. Since the configuration around each of the photoconductors 1Y, 1C, 1M, and 1K is the same, only one photoconductor 1 is illustrated, and reference numerals Y, C, M, and K for color coding are omitted. As shown in FIG. 2, around the photosensitive member 1, a charging roller 2 as a charging unit, a developing device 4 as a developing unit, and a toner scattering member 5 are sequentially arranged along the surface movement direction. The charging roller 2 is disposed in a non-contact manner while maintaining a gap with the photoconductor 1 and uniformly charges the surface of the photoconductor 1. The developing device 4 includes a developing roller 4a, a pair of agitators 4b, and the like, and stores a two-component developer composed of toner and a carrier. In the cleaner-less method, charging with the charging roller 2 and exposure with the laser beam L are performed in a state where the residual toner after passing through the primary transfer portion adheres to the surface of the photoreceptor 1, and an electrostatic latent image is formed. Then, the developing device 4 performs development by supplying new toner in addition to the already existing residual toner to the exposed portion subjected to the current exposure, while developing the transfer residual toner existing in the unexposed portion. It is recovered by flying to the apparatus 5 side, that is, cleaning and recycling of residual toner in an unexposed portion is performed.

  The development of the exposed portion and the cleaning of the unexposed portion performed simultaneously in the developing device 4 are based on the following principle. That is, in the reversal development method, from the developing device 4 in which a voltage having a value lower than the charging potential of the photosensitive member (unexposed portion) 1 is applied to the exposed portion where the surface potential is reduced to near zero, The toner charged to the same polarity (negative polarity) as the charged polarity of 1 is supplied for development. At this time, the residual toner present in the unexposed portion of the photoreceptor 1 is recovered by flying from the photoreceptor 1 to the developing device 4 due to the potential difference between the photoreceptor 1 and the charging roller 2. As described above, the transfer residual toner is collected by the developing device 4 and reused for development, so that it is not necessary to provide a waste toner tank for storing the toner collected by cleaning from the photoreceptor 1, and an image forming apparatus or the like. Can be miniaturized. In particular, in a tandem color image forming apparatus in which four photoconductors 1 are arranged in parallel, the size can be significantly reduced as compared with the case where individual waste toner paths are provided for each photoconductor 1. Furthermore, the cost can be reduced by recycling the toner, so that the running cost can be reduced and the maintainability can be improved for the user.

  As the developing device 4, it is preferable to use two-component development comprising a carrier and toner as a developer. The positively charged transfer residual toner adheres to the positively charged carrier and is collected in the developing device 4. In addition, the toner on the photoconductor is easily recovered mechanically by the rubbing of the magnetic brush with the photoconductor in the developing region. On the other hand, a one-component developing device composed only of toner may be used as the developing device. In this case, there is an advantage of downsizing and cost reduction, and the transfer residual toner that is normally charged by the contact pressure and electric field between the photosensitive member and the developing roller is collected in the developing device.

  Next, the characteristics of the toner used in this embodiment will be described. The toner used in this embodiment preferably has a volume average particle size of 4 to 10 μm. When a small particle diameter toner having an average particle diameter of 10 μm or less can be used, the bulk density of the developer can be increased, so that the agent can be stably stirred and conveyed, and the recovery efficiency of the transfer residual toner can be improved. In addition, since the particle size distribution is sharp, the developer has good fluidity, and it is possible to perform a stable agent circulation over a long period of time, thereby improving the replenishment toner diffusibility. On the other hand, since the gap between the toners becomes smaller and the toner becomes more solid in the image, the required toner adhesion amount and the height (pile height) of the toner image can be reduced. In addition, regarding the reproducibility of minute dots of 600 dpi or more, in this range, toner particles having a sufficiently small particle diameter are contained in a minute latent image dot, so that dot reproducibility is excellent and image stability is improved. Becomes higher. On the other hand, when the volume average particle diameter is less than 4 μm, phenomena such as a decrease in transfer efficiency and a decrease in recoverability with a brush tend to occur. When the volume average particle size exceeds 10 μm, the pile height of the image becomes large, and it becomes difficult to suppress scattering of characters and lines. At the same time, the ratio (D4 / D1) of the weight average particle diameter (D4) to the number average particle diameter (D1) is preferably in the range of 1.00 to 1.30. The closer (D4 / D1) is to 1.00, the sharper the particle size distribution. With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do.

  A method for measuring the particle size distribution of the toner particles will be described. Examples of the measuring device for the particle size distribution of toner particles by the Coulter counter method include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter). The measurement method is described below. First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measurement device is used to measure the volume and number of toner particles or toner using a 100 μm aperture as an aperture. Volume distribution and number distribution are calculated. From the obtained distribution, the weight average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.

Further, the toner used in this embodiment preferably has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180. 3 and 4 are schematic diagrams schematically showing the shape of the toner in order to explain the shape factor SF-1 and the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4. When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner onto the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π. When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.
SF-2 = {(PERI) ² / AREA} × (100 / 4π) (2)

  Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.) and introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) for analysis. Calculated. When the shape of the toner is close to a spherical shape, the contact state between the toners becomes point contact, so that the adsorbing force between the toners is weakened, and thus the fluidity is increased, and the stirring efficiency of the agent and the toner is improved. In addition, since the contact state between the toner and the photoconductor is a point contact, the attractive force between the toner and the photoconductor is weakened, and the transfer rate is increased, contributing to the improvement in image quality. On the other hand, if any of the shape factors SF-1 and SF-2 exceeds 180, the fluidity is deteriorated, and the agent circulation property and the replenishment toner diffusibility are poor. Further, the transfer rate is lowered, the thinning is not stable, and the charge injection becomes unstable, which is not preferable.

In addition, the toner used in the exemplary embodiment is obtained by attaching fine particles (hereinafter, simply referred to as fine particles) having an average primary particle size of 50 to 500 nm and a bulk density of 0.3 mg / cm ³ or more to the particle surface of the toner. is there.
Bulk density (g / cm ³ ) = fine particle amount (g / 100 ml) ÷ 100
In addition, although silica etc. are often used for a normal fluid improvement agent, for example, the average primary particle diameter of this silica is 10-30 nm normally, and a bulk density is 0.1-0.2 mg / cm < ³ >. In the present embodiment, the presence of fine particles having appropriate characteristics on the surface of the toner forms an appropriate gap between the toner particles and the object. In addition, fine particles have a very small contact area with toner particles, a photoconductor, a conveyance belt, etc., and are evenly contacted, so the effect of reducing adhesion is great, and toner of an unfixed image facing the conveyance belt adheres to the conveyance belt. There is little disturbance of the image because it is difficult. In addition, since the development / transfer efficiency is improved and the dot reproducibility is improved, the image is stabilized and a margin is increased against disturbance during conveyance. In addition, since it is difficult to embed in the toner particles, or can be detached and restored even if it is slightly buried, stable characteristics can be obtained over a long period of time. Since these characteristics have an effect of reducing the share received by the toner particles, the filming effect of the toner itself due to the low rheological component contained in the toner is exhibited for high-speed fixing (low energy fixing). Further, although the details are not clear, even if the surface-treated fine particles are externally added to the toner or the carrier is contaminated, the degree of developer deterioration is small. Accordingly, since the change in the fluidity and charging property of the toner is small over time, the developer circulation and the replenishment toner diffusion can be stably performed over a long period of time. Also, the stability of image quality is increased.

The average primary particle size (hereinafter referred to as the average particle size) of the fine particles used in the present embodiment is 50 to 500 nm, and preferably 100 to 400 nm. If the thickness is less than 50 nm, the fine particles may be buried in the concave and convex portions on the toner surface to lower the role of the rollers. On the other hand, if it is larger than 500 μm, it becomes an order of the same level as the contact area of the toner itself, and the roller effect on the toner is reduced. When the bulk density is less than 0.3 mg / cm ³ , although there is a contribution to improving the fluidity, the scattering properties and adhesion of the toner and fine particles are increased, so that the effects and functions of the toner and roller are reduced. . In the fine particles used in the present embodiment, as the inorganic compound, SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , BaO, CaO, K ₂ O, Na Examples include ₂ O, ZrO ₂ , CaO · SiO ₂ , K ₂ O (TiO ₂ ) _n , Al ₂ O ₃ · 2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO ₄ , SrTiO _{3, and the} like. _{preferably, SiO 2, TiO 2, Al} 2 O 3 and the like. In particular, these inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like. The organic compound fine particles may be a thermoplastic resin or a thermosetting resin. For example, vinyl resin, polyurethane resin, epoxy resin, polyester resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin, Examples include urea resins, aniline resins, ionomer resins, and polycarbonate resins. As the resin fine particles, two or more of the above resins may be used in combination. Of these, vinyl resins, polyurethane resins, epoxy resins, polyester resins, and combinations thereof are preferred because an aqueous dispersion of fine spherical resin particles is easily obtained. Specific examples of vinyl resins include polymers obtained by homopolymerization or copolymerization of vinyl monomers, such as styrene- (meth) acrylic acid ester copolymers, styrene-butadiene copolymers, (meth) acrylic acid. -Acrylic ester copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, and the like. The fine particles described above can be externally added and adhered to the toner surface by a method in which the toner base particles and the fine particles are mechanically mixed and adhered using various known mixing devices, or in the liquid phase. There is a method in which particles and fine particles are uniformly dispersed with a surfactant or the like, and are dried after an adhesion treatment.

  Next, the configuration of the charging roller 2 will be described. FIG. 5 is a cross-sectional view showing the configuration of the photoreceptor and the charging roller. As shown in FIG. 5, the charging roller 2 includes a shaft portion 2a, a main body portion 2b formed outside the shaft portion 2a, and spacer members 2c provided at both longitudinal ends of the shaft portion 2a. The charging roller 2 is disposed in close proximity with a predetermined gap (20 μm to 80 μm) between the main body 2b and the photoreceptor 1 by the spacer member 2c, and the surface of the photoreceptor 1 is fixed by causing proximity discharge with the photoreceptor 1. Charge to potential. In the present embodiment, the charging roller 2 has an outer diameter of 12 mm and is close to the photoreceptor 1 with a gap of 50 μm. Then, a negative charging bias Vc in which an AC voltage and a DC voltage are superimposed is applied to the charging roller 2 so that the surface potential of the photoreceptor 1 becomes −600V.

  Further, as shown in FIG. 2, a guard member 3 is installed around the charging roller 2 with a gap of 1 to 5 mm from the charging roller 2. The guard member 3 is made of a metal such as aluminum, stainless steel, or iron, or a resin containing a conductive agent, and is connected to a power source and applied with a bias Vg. Since a charging bias Vc containing an AC component is applied to the charging roller 2, the toner attached on the charging roller 2 flies back to the photosensitive member 1 due to the AC voltage, and contamination of the charging roller 2 is a problem. Don't be. The guard member 3 prevents the toner vibrated by the alternating voltage from flying and contaminates the members around the charging roller 2 and at the same time returns the toner accumulated in the guard member 3 to the charging roller 2. Yes.

FIG. 6 is a radial cross-sectional view showing the configuration of the charging roller. As shown in FIG. 6, the main body 2b of the charging roller 2 has a resistance adjusting layer 2d on the outer side of the shaft 2a and a protective layer 2e on the outermost layer. The shaft portion 2a is made of, for example, stainless steel having a diameter of 8 to 20 mm, aluminum having high rigidity and conductivity, or 1 × 10 ³ Ω · cm or less, preferably 1 × 10 ² Ω · cm or less. And composed of a conductive resin having high rigidity. The resistance adjusting layer 2d has a volume resistivity of 1 × 10 ⁵ Ω · cm to 1 × 10 ⁹ Ω · cm, and preferably has a thickness of about 1 to 2 mm. The protective layer 2e has a volume resistivity of 1 × 10 ⁶ Ω · cm to 1 × 10 ¹⁰ Ω · cm, and preferably has a thickness of about 10 μm. The volume resistivity of the protective layer 2e is preferably higher than the electrical resistivity of the resistance adjustment layer 2d.

  Conventionally, a rubber such as hydrin rubber has been used for the resistance adjustment layer 2d. However, in this embodiment, a polymer ion conductive material is used as a resin having a lower expansion coefficient than rubber and capable of maintaining dimensional accuracy in the initial stage and over time. The thermoplastic resin composition containing is used. As the base resin that composes the thermoplastic resin composition, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, acrylonitrile-styrene copolymer, and acrylonitrile-butadiene copolymer can be used. The polymer type ion conductive material contained in the thermoplastic resin composition is preferably composed of a polymer compound containing a polyether ester amide component.

  The protective layer 2e is made of a resin selected from acrylic silicon resin, fluorine resin, silicone resin, acrylic resin, polyamide resin, polyurethane resin, polyester resin, and polyvinyl butyral resin. Since these resins are excellent in non-adhesiveness, a charging roller excellent in toner adhesion can be obtained. Further, since these resins are electrically insulative, if the protective layer 2e is formed alone, the characteristics as the charging roller 2 cannot be obtained. Therefore, in the present embodiment, the resin composition forming the protective layer contains conductive particles. For example, metal oxides such as tin oxide and iron oxide, and carbon black such as acetylene black and ketjen black are preferably used.

  The space member 2c of the charging roller 2 is made of polyethylene resin or the like. In particular, by using a polyethylene resin having a molecular weight of 1,000,000 or more, a stable gap can be maintained between the photosensitive member and the main body of the charging roller even when used for a long time. The reason why the resin can be used for the charging roller 2 is that the charging roller 2 is installed in a non-contact manner. If a resin is used in the case of a contact charging roller, the charging nip is not stable due to lack of elasticity, and the photosensitive member cannot be uniformly charged. In the cleanerless system in which the toner input to the charging roller is large, by making the charging roller 2 non-contact, it is possible to use a resin that is excellent in durability and hardly adheres to the toner.

  Next, the transfer residual toner remaining on the surface of the photoconductor 1 after the toner image on the photoconductor 1 is transferred to the transfer belt 10 will be described. Among the transfer residual toners, there are a normally charged toner T0 charged to a normal polarity and a reverse charged toner T1 charged to a polarity opposite to the normal polarity. FIG. 7A is a characteristic diagram showing the toner charge amount distribution immediately before the transfer of the toner carried on the photosensitive member. FIG. 7B is a characteristic diagram showing the toner charge amount distribution of the untransferred toner remaining on the photoreceptor 1 after the transfer. As shown in FIG. 7 (a), the charge amount of the toner immediately before the transfer is distributed around -30 (μC / g), and most of the charge toner T0 is normally charged negatively. It is. On the other hand, as shown in FIG. 7B, the charge amount of the transfer residual toner is distributed around about −2 (μC / g). Part of the untransferred toner has its toner charging polarity reversed to positive polarity due to discharge due to a potential difference between the positive polarity bias applied to the primary transfer roller 14 and the potential of the photosensitive member 1 in the vicinity of the transfer region. As a result, the reverse transfer toner T1 that has been reversed to the positive polarity as indicated by the shaded portion in FIG. 7B exists in the transfer residual toner. When such a reversely charged toner T1 is conveyed to the charging region of the charging roller 2 while adhering to the photoreceptor 1, it is electrostatically attracted to the surface of the charging roller 2 to which a negative charging bias is applied. Although attached, it receives vibration due to the AC voltage applied to the charging roller 2 and returns from the charging roller 2 to the photoreceptor 1. Since the charging roller 2 is installed in a non-contact manner on the photosensitive member 1, the toner adhering to the charging roller 2 can return to the photosensitive member 1 without being crushed. Roller dirt is not a problem. The charge distribution of the toner after passing through the charging roller 2 is shifted to the weakly charged side due to the influence of the AC voltage of the charging roller 2 regardless of the charge distribution at the time of input to the charging roller 2. Due to the weak charging of the toner, the mirror image force between the photosensitive member 1 and the toner is weakened, so that the development recovery of the toner is enhanced. However, if the amount of transfer residual toner input to the charging roller 2 is remarkably large, there is also a strong regular charged toner, which is difficult to collect. This normally charged toner that could not be collected causes afterimages. In order to suppress this afterimage, the toner scattering member 5 is indispensable.

Hereinafter, the configuration of the toner scattering member will be described based on specific examples.
[Example 1]
FIG. 8 is a configuration diagram showing the configuration of the toner scattering brush. As shown in FIG. 8, a conductive brush using fibers such as acrylic, nylon, and PET blended with a conductive material such as carbon black is used as the toner scattering brush 5A. The toner scattering brush 5A includes a brush portion 50 and a support portion 51 that supports the brush portion 50 and swings in the longitudinal direction. The brush portion 50 of the toner scattering member 5A has a length in the longitudinal direction shorter than the length in the axial direction of the photoreceptor 1 and longer than the length in the axial direction of the developing roller 4a. In the toner scattering brush 5 </ b> A, the brush portion 50 is swung in the longitudinal direction by the support portion 51, and the transfer residual toner on the photoreceptor 1 is scattered in the longitudinal direction. As a result, much toner does not remain locally on the photoreceptor 1. However, by simply swinging the toner scattering brush 5A (the brush potential is grounded), the toner moving distance is short (corresponding to the swinging width), and although the boundary is blurred, depending on the output image such as a thick band chart. An afterimage may remain. The transfer residual toner is once collected by the toner scattering brush 5A and discharged at a certain timing, whereby the moving distance of the toner can be increased.

  For example, the toner scattering brush 5A may collect at least a part of the transfer residual toner in the image forming region and discharge at least a part of the transfer residual toner accumulated between the papers. Here, the image forming area is an area to be transferred to the transfer paper, and the inter-paper space is an area other than the image forming area. Alternatively, the toner scattering brush 5A may collect at least a part of the transfer residual toner in the image part and discharge at least a part of the transfer residual toner accumulated in the non-image part. Here, the image portion is a region where an image is present in any region in the photosensitive member axial direction, and the non-image portion is a region where no image is present in any region in the photosensitive member axial direction, and includes a space between sheets. After the transfer residual toner on the photoreceptor 1 passes through the charging roller 2, the transfer toner where a large amount of transfer residual toner remains is moved to a place where the transfer residual toner is small, so that the residual image can be suppressed. It is most desirable that the transfer destination (transfer area) of the transfer residual toner is between the sheets. If the transfer destination of the transfer residual toner is between sheets, even if an afterimage is generated on the photosensitive member 1, the output image is not affected.

  As will be described later, the toner scattering brush 5A can vary parameters such as applied bias and contact pressure, and can easily control the collection and discharge of the residual toner. The collection and discharge of the transfer residual toner by the toner scatter brush 5A controls the bias applied to the toner scatter brush 5A, and changes the potential difference between the DC component of the bias applied to the toner scatter brush 5A and the potential of the photoreceptor 1. Can be done. When the charge distribution of the transfer residual toner is closer to the negative electrode side, the applied bias applied to the toner scattering brush 5A is (DC component of bias applied in the image forming area)> (DC component of bias applied between papers). It is recommended that Alternatively, (DC component of applied bias in image portion)> (DC component of applied bias in non-image portion) may be satisfied. When the charge distribution of the transfer residual toner is closer to the positive electrode side, the applied bias applied to the toner scattering brush 5A is (DC component of bias applied in the image forming region) <(DC component of bias applied between papers). It is recommended that Alternatively, (DC component of applied bias in the image portion) <(DC component of applied bias in the non-image portion) may be satisfied. By setting such a potential difference, the transfer residual toner can be collected in the image forming area or the image portion, and the transfer residual toner can be discharged between the sheets or in the non-image portion, so that the transfer residual toner can be scattered.

  Further, the collection and discharge of the transfer residual toner by the toner scattering brush 5A can be effectively controlled by changing the frequency of the AC component of the bias applied to the toner scattering brush 5A. The toner scattering brush 5 </ b> A is more likely to discharge the untransferred toner when the low frequency AC component is applied in a superimposed manner than when only the DC component is applied. For example, the AC component of the bias applied to the toner scattering brush 5A may not be present in the image forming region or the image portion, and the AC component of the bias applied to the toner scattering brush 5A may be present between the sheets or in the non-image portion. Alternatively, an AC component may be superimposed on the applied bias applied to the toner scattering brush 5A in either the image forming region or image portion and between the paper or the non-image portion. In this case, (applied bias frequency in the image forming region)> (applied bias frequency between sheets) is preferably satisfied. Alternatively, (applied bias frequency in the image portion)> (applied bias frequency in the non-image portion) may be satisfied. When an AC component having a frequency lower than the high frequency is applied, the transfer residual toner is more easily discharged from the toner scattering brush 5A.

[Example 2]
FIG. 9A is a configuration diagram for explaining the positional relationship between the toner-spreading blade and the photoconductor in the image forming area, and FIG. 9B shows the positional relationship between the toner-spreading blade and the photoconductor between the sheets. It is a block diagram. FIG. 10 is a cross-sectional view showing a configuration of an eccentric cam used in the toner scattering blade. As shown in FIGS. 9 and 10, the toner scattering blade 5B includes a blade 52 using an elastic material such as urethane rubber, an arm 53 that supports the blade 52 at one end with a fulcrum 53a as a center, and the arm 53 as a photosensitive member. A spring 54 that biases in the direction and an eccentric cam 55 that contacts the other end of the arm 53 at a predetermined timing and biases in the direction opposite to the biasing direction of the spring 54 are provided. The toner scattering blade 5B can change the contact pressure between the photosensitive member 1 and the blade 52 by changing the angle of the blade 52 using the rotation of the spring 54 and the eccentric cam 55. As shown in FIG. 9A, in the image forming region or image portion, the contact pressure between the photosensitive member 1 and the blade 52 is increased by the biasing by the spring 54, and the transfer residual toner is collected on the blade 52. On the other hand, between the sheets or in the non-image area, the photosensitive member 1 and the blade 52 are temporarily separated by the urging by the eccentric cam 55 and the transfer residual toner is discharged from the blade 52. Even if a large amount of toner flows from the gap between the photosensitive member 1 and the blade 52, the charging roller 2 is not contaminated due to the self-cleaning effect of the charging roller 2. Since the blade is inexpensive, it leads to cost reduction. The adjustment of the gap between the photosensitive member 1 and the blade 52 is not limited to the clutch mechanism as shown in FIG. 9, and other mechanisms may be used. Further, the toner collection in the image forming region or the image portion and the toner discharge in the interval between the paper or the non-image portion by the toner scattering blade 5B are the DC component of the bias applied to the toner scattering blade as in the first embodiment. Control may be performed by changing the potential difference from the potential of the photoreceptor or the frequency of the AC component of the applied bias.

[Example 3]
FIG. 11 is a configuration diagram showing the configuration of the toner scattering roller. As shown in FIG. 11, a roller having the same form as the charging roller 2 can be used as the toner scattering roller 5 </ b> C. The toner scattering roller 5C is made of a material having a small adhesion force to the toner (same as the characteristics of the charging roller 2 described above), and the gap with the photosensitive member 1 is maintained with high accuracy. The toner does not adhere to 5C. The toner scattering roller 5C is less likely to change the amount of collected / discharged residual toner over time. The toner recovery in the image forming region or image portion and the toner discharge in the interval between papers or in the non-image portion are the same as in Example 1 except that the potential difference between the DC component of the bias applied to the toner scattering blade and the potential of the photosensitive member Alternatively, it may be controlled by changing the frequency of the AC component of the applied bias.

Hereinafter, an embodiment in which toner is collected and discharged using the toner scattering roller 5C will be described.
(1) When there is a large amount of toner on the negative polarity side in the charge distribution of the transfer residual toner as shown in FIG. 7B, it is desired to collect a larger amount of negative polarity toner in the image forming region. An applied bias (for example, +300 V) was applied. In order to discharge the collected toner between the sheets, a negative (for example, −300 V) applied bias was applied to the toner scattering roller 5C. However, when only the DC component is applied, all the toner cannot be discharged. Therefore, when the AC component (for example, 100 Hz, 600 Vpp) was superimposed on the DC component (−300 V), the toner was successfully discharged from the toner scattering roller 5C.

(2) In the charge distribution of the transfer residual toner, the toner scattering roller 5C in the image forming region is opposite to the case of FIG. 7B in which the y-axis is symmetric, that is, when the toner on the positive polarity side is large. A negative (for example, -300 V) applied bias was applied to. Between the papers, an applied bias in which an AC component (eg, 100 Hz, 600 Vpp) is superimposed on a positive DC component (eg, +300 V) is applied to the toner scattering roller 5C. As a result, it was possible to successfully collect toner in the image forming area and discharge toner between sheets.

(3) When the transfer residual toner is strongly charged Since the transfer residual toner cannot be recovered unless the charge of the transfer residual toner is weakened, an applied bias in which an AC component is superimposed is applied to the toner scattering roller 5C in the image forming region. Since the AC transfer component causes the transfer residual toner to be weakly charged, the transfer residual toner can be successfully collected by the toner scattering roller 5C. However, it is difficult to collect the transfer residual toner unless the AC frequency in the image forming area is increased. For example, when the frequency is 2000 Hz, the toner can be weakly charged and recovered at the same time. Between the papers, an AC component of about 100 Hz was superimposed as described in (1) and (2) so that the untransferred toner was discharged from the toner scattering roller 5C. The transfer residual toner is more easily discharged when an AC component having a lower frequency than a high frequency is applied.

[Example 4]
As shown in FIG. 2, the toner scattering brush roller 5D according to the fourth embodiment is a conductive brush using fibers such as acrylic, nylon, and PET in which a conductive material such as carbon black is blended. The toner scattering brush roller 5D can swing all the parameters of the rotational speed (linear speed difference with the photosensitive member), the applied bias Vcl, and the contact pressure, and collects the toner in the image forming area or the image area, and between the paper Alternatively, it is easy to control the toner discharge in the non-image area. For example, the rotational speed of the toner scattering member 5D is expressed as follows: | Linear speed difference between the photosensitive member 1 and the toner scattering brush roller 5D in the image forming area | <| Line between the photosensitive member 1 and the toner scattering brush roller 5D between papers By setting the speed difference |, toner collection and discharge can be controlled. In the present embodiment, in the image forming region, the toner recovery performance by the toner scatter brush roller 5D is considerably improved by setting the linear velocity difference between the photoreceptor 1 and the toner scatter brush roller 5D to 0 mm / s. Further, when the linear velocity difference between the photosensitive member 1 and the toner scattering brush roller 5D is set to 500 mm / s between the sheets, the toner is easily discharged from the toner scattering brush roller 5D. The linear speed difference may be adjusted by changing the number of rotations of the motor that drives the toner scatter brush roller 5D, but the connection between the motor and the toner scatter brush roller 5D is cut off in the image forming area using a clutch. It is also possible to bring the difference in linear velocity closer to 0 mm / s by turning the toner-scattering brush roller 5D in the accompanying state. The bias application control to the toner scattering brush roller 5D may be performed in the same manner as in the third embodiment.

As described above, according to the printer according to the present embodiment, the charging roller 2 is arranged in a non-contact state with the photosensitive member 1 and a voltage including an AC component is applied, so that the charging roller 2 itself performs self-cleaning. The toner can hardly adhere to the charging roller 2. Further, before the transfer residual toner remaining on the photosensitive member 1 passes through the charging roller 2, the toner scattering member 5 (A, B, C, D) moves the toner where the transfer residual toner is large to a small amount. Scatter the transfer residual toner. As a result, the transfer residual toner can be weakly charged by the charging roller evenly, so that the toner recoverability by the developing device 4 is improved and the occurrence of a residual image is suppressed.
Further, according to the printer according to the present embodiment, the toner scattering member 5 (A, B, C, D) collects the transfer residual toner in the image forming area and transfers the transfer residual between the papers without the transfer residual toner. By discharging the toner, the toner with a large amount of transfer residual toner is moved to a small place. As a result, the transfer residual toner can be uniformly weakly charged by the charging means, and the occurrence of a residual image can be suppressed. Even if an afterimage occurs, the output image is not affected if there is a gap between sheets.
Further, according to the printer according to the present embodiment, the toner scattering member 5 (A, B, C, D) collects the transfer residual toner in the image portion and transfers the transfer residual toner in the non-image portion where there is no transfer residual toner. By discharging the toner, the toner having a large amount of transfer residual toner is moved to a position having a small amount. As a result, the transfer residual toner can be weakly charged uniformly by the charging roller 2, and the occurrence of a residual image can be suppressed.
Further, according to the printer of the present embodiment, the potential difference between the DC component of the voltage applied to the toner scattering member 5 (A, B, C, D) and the potential of the photosensitive member is the image forming area or image portion, and the paper. It is different between or non-image part. Thereby, it is possible to control the toner collection in the image forming area or the image portion and the toner discharge in the interval between the sheets or in the non-image portion.
Further, according to the printer according to the present embodiment, when the charge distribution of the transfer residual toner is closer to the negative electrode side, the toner is applied to the toner scattering member 5 (A, B, C, D) in the image forming region or the image portion. The DC component of the voltage is larger than the DC component of the voltage applied to the toner scattering member 5 between the papers or in the non-image area. In addition, when the charge distribution of the transfer residual toner is closer to the positive electrode side, the DC component of the voltage applied to the toner scattering member 5 (A, B, C, D) in the image forming area or image portion is between paper or non-image. This is smaller than the direct current component of the voltage applied to the toner scattering member 5 (A, B, C, D). In this way, by setting a potential difference between the image forming area or image portion and the paper interval or non-image portion, toner collection in the image forming region or image portion and toner discharge between the paper or non-image portion are controlled. can do.
Further, according to the printer according to the present embodiment, the frequency of the AC component of the voltage applied to the toner scattering member 5 (A, B, C, D) is such that the image forming area or the image portion and the paper interval or the non-image portion. And is different. Thereby, it is possible to control the toner collection in the image forming area or the image portion and the toner discharge in the interval between the sheets or in the non-image portion.
Further, according to the printer according to the present embodiment, the voltage applied to the toner scattering member 5 (A, B, C, D) has no AC component in the image forming region or the image portion, and is between the paper or the non-image portion. There is an AC component. In the interval between sheets or in the non-image portion, it is easier to discharge the toner by applying a voltage in which an AC component is superimposed on the toner scattering member 5 (A, B, C, D).
Further, according to the printer according to the present embodiment, the voltage applied to the toner scattering member 5 (A, B, C, D) can be applied both in the image forming area or the image portion and between the paper and the non-image portion. The AC component is superimposed, and the frequency of the AC component of the applied voltage in the image forming region or the image part is higher than the frequency of the AC component of the applied voltage between the sheets or in the non-image part. In the inter-paper or non-image area, the toner is more easily discharged when a low frequency is applied to the toner scattering member 5 (A, B, C, D) than a high frequency.
Further, according to the printer according to the present embodiment, the toner scattering member 5 (A, B, D) has different contact pressures with the image carrier between the sheets or between the non-image area and the image forming area or image area. Thereby, it is possible to control the toner collection in the image forming area or the image portion and the toner discharge in the interval between the sheets or in the non-image portion.
Further, according to the printer according to the present embodiment, the toner scattering member 5 (A, B, D) is configured such that the contact pressure on the image carrier in the image forming region or the image portion is between the paper or in the non-image portion. Greater than the contact pressure to the carrier. The higher the contact pressure between the photosensitive member 1 and the toner scattering member 5 (A, B, D), the higher the toner recoverability, and the lower the contact pressure, the higher the toner discharge performance.
Further, according to the printer according to the present embodiment, the toner scattering member 5D is composed of a rotating body, and the number of rotations of the rotating body is different between sheets or between a non-image area and an image forming area or an image area. Thereby, it is possible to control the toner collection in the image forming area or the image portion and the toner discharge in the interval between the sheets or in the non-image portion.
Further, according to the printer according to the present embodiment, the linear velocity difference between the photosensitive member 1 and the toner scattering member 5D is larger between the sheets or in the non-image portion than in the image forming region or the image portion. The smaller the linear velocity difference between the photosensitive member 1 and the toner scattering member 5D, the higher the toner recoverability, and the larger the linear velocity difference, the higher the toner ejection performance.
Further, according to the printer of this embodiment, the toner scattering brush 5A and the toner scattering brush roller 5D can be used as the toner scattering member. The toner scattering brush 5A can swing parameters such as applied bias and contact pressure, and can easily control toner collection and toner ejection. The toner scattering brush roller 5D can vary parameters such as the number of rotations, applied bias, and contact pressure, and can easily control toner collection and toner ejection.
Further, according to the printer according to the present embodiment, the toner scattering blade 5B can be used as the toner scattering member. Since the toner scattering blade 5B is inexpensive, cost reduction can be achieved.
Further, according to the printer of this embodiment, the toner scattering roller 5C can be used as the toner scattering member. The toner scattering roller 5C is less likely to change the amount of toner collected and discharged over time.
Further, according to the printer according to the present embodiment, the toner scattering roller 5C is arranged in a non-contact manner while maintaining a gap with the photoreceptor 1. Therefore, it is possible to suppress adhesion of foreign matters such as toner to the toner scattering roller 5C.
Further, according to the printer of this embodiment, the effect of scattering in the longitudinal direction is enhanced by swinging the toner scattering brush 5A and the toner scattering blade 5B in the longitudinal direction.

1 is a schematic configuration diagram illustrating an internal configuration of a printer according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating a configuration around a photoconductor of the printer. FIG. 4 is a schematic diagram schematically illustrating the shape of a toner for explaining a shape factor SF-1. FIG. 4 is a schematic diagram schematically illustrating the shape of a toner for explaining a shape factor SF-2. FIG. 3 is a cross-sectional view illustrating a configuration of a photoconductor and a charging roller of the printer. FIG. 3 is a radial cross-sectional view illustrating a configuration of the charging roller. (A) is a characteristic diagram showing a toner charge amount distribution immediately before transfer of toner carried on the photoreceptor, and (b) is a toner charge amount distribution of residual toner remaining on the photoreceptor 1 after transfer. Characteristic diagram. 1 is a configuration diagram illustrating a configuration of a toner scattering brush according to Embodiment 1. FIG. (A) is a block diagram for explaining the positional relationship between the toner-spreading blade and the photoconductor in the image forming area, and (b) is a block diagram for explaining the positional relationship between the toner-spreading blade and the photoconductor between the sheets. . Sectional drawing which shows the structure of the eccentric cam used for a toner scattering blade. FIG. 3 is a configuration diagram illustrating a configuration of a toner scattering roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 3 Guard member 4 Developing device 5 Toner scattering member 5A Toner scattering brush 5B Toner scattering blade 5C Toner scattering roller 5D Toner scattering brush roller

Claims (1)

An image carrier for carrying an image, a charging unit for charging the image carrier, a latent image forming unit for forming a latent image on the image carrier, and supplying toner to the latent image on the image carrier for development In addition, in an image forming apparatus comprising: a developing unit that collects toner remaining on the image carrier; and a transfer unit that transfers a toner image on the image carrier to a transfer target.
The charging means is arranged such that the charging member is maintained in a non-contact state with the image carrier, and charges the image carrier using a discharge generated by applying a voltage in which an alternating current component is superimposed on a direct current component. ,
A toner scattering member that disperses residual toner remaining on the image carrier without being transferred by the transfer unit is located upstream of the charging unit in the moving direction of the image carrier, and is more upstream than the transfer unit. Prepare for the downstream side of the moving direction,
In the image forming apparatus, the toner scattering member has a contact pressure on the image carrier in the image forming region or in the image portion that is greater than a contact pressure on the image carrier in between the sheets or in the non-image portion .

Images